Metal-porcelain dental restorations, dental veneers, dental bridges and metal foil for use therein and methods for making dental appliances

ABSTRACT

A metal porcelain dental restoration for filling an edentulous region is provided. The dental restoration comprises a first layer of a thin metal foil which closely fits the contours of the two abutment teeth on either side of the edentulous region, a layer of ceramic on the first metal foil layer, a second layer of thin metal foil connected to the ceramic layer and extending at least across the joint from the abutment teeth to the edentulous region and a ceramic build-up to fill the edentulous region.

This is a continuation of application Ser. No. 480,557 filed Feb. 14,1990, now U.S. Pat. No. 4,997,723, which is a continuation-in-part of mycopending application Ser. No. 049,119 filed May 13, 1987, nowabandoned.

FIELD OF THE INVENTION

This invention relates to improved metal-porcelain dental restorations,improved metal-porcelain dental veneers, improved dental bridges and animproved metal foil for use in such dental applications.

BACKGROUND OF THE INVENTION

It is a goal in the art of artificial porcelain dental restorations andveneers to match as closely as possible the appearance of the patient'ssurrounding natural dentition. In particular it is desirable for thecolor of the artificial restoration or veneer to match as closely aspossible the color of the adjacent teeth. As natural tooth color variesamong individuals, it is necessary for the dental technician or dentistto be able to control the color to properly match the natural teeth ofeach individual patient.

There are many types of porcelain dental restorations. The techniqueused for color matching will vary depending on the type of porcelainrestoration made. Modern porcelain restorations typically includeporcelain bonded to an underlying metal substructure. The porcelaintypically includes an opaque base layer, an intermediate layer of dentinporcelain, and an outer layer of enamel porcelain. In some cases, themetal substructure is covered with a bonding agent to promote bonding ofthe porcelain to the metal. The color of the completed restoration is afunction of the color and opacity of the opaque, dentin, and enamellayers of the porcelain, the color of the metal substructure, and thecolor of the bonding agent in cases where it is used. In theserestorations, the dental technician adjusts the color of the totalrestoration by adjusting the colors of each of the components of therestoration. Most often, the underlying metal substructure gives anunappealing grayish cast to the restoration. Attempts to hide the graycolor result in a thicker and more opaque porcelain which tends to lookunnatural when compared to the natural translucency of human teeth. Thisis particularly true in cases where very thin restorations are used.

A new type of metal porcelain restoration has been introduced asdescribed in U.S. Pat. No. 4,392,829, issued July 12, 1983, the completedisclosure of which is incorporated herein by reference. That inventionrelates to a dental restoration wherein the metal substructure is a thinplatinum foil having a textured surface to which porcelain is directlyapplied. The foil is swaged over a die of the tooth, the foil is sandblasted to texturize the surface, porcelain paste is applied directly tothe textured surface of the foil, and the restoration is baked to hardenthe porcelain and bond it to the foil. The invention eliminates the needfor the application of a bonding agent to the foil, which had previouslybeen necessary to promote adhesion of the porcelain to the foil. Theplatinum foil, however, has a gray appearance which presents the samecolor matching problems experienced in restoration of the prior art.

Dental bridges are a kind of porcelain dental restoration designed tofill edentulous regions. Existing dental bridges suffer the sameshortcomings as other dental restorations. In addition, because of thegreater size, dental bridges have additional breakage problems. Inparticular, at the joints between the teeth on either side of theedentulous region and the edentulous region itself, the metal is thinand often breaks.

Rather than using an entire dental restoration, dental veneers aresometimes used when it is desirable to replace worn-down portions ofteeth or to attempt to provide a more desirable color to a discoloredtooth.

There are various types of conventional dental veneers, all aretypically made entirely of porcelain without the inclusion of a metalsubstructure. The conventional veneers generally have three porcelainlayers: an opaque base layer, an intermediate layer of dentin porcelain,and an outer layer of enamel porcelain. Typically, these veneers have atotal thickness of greater than 500 microns.

These dental veneers are bonded to the patient's natural tooth by firstetching the surface of the tooth to promote bonding. This etchingtechnique is well known in the art. After etching, the porcelain dentalveneer is bonded to the tooth surface using a bonding agent. The use ofthese all-porcelain veneers does not mask sever discoloration of theunderlying tooth and is also affected by the color of the bondingmaterial. Moreover, the veneer does not have great strength by itself.Thin veneers, which are more desirable from an aesthetic viewpoint, areeasily broken when being bonded. Furthermore, in a posterior occlusalusage, the tooth must be ground extensively to allow the use of athicker occlusal onlay or a crown. While a platinum or palladium foilcould be used as the metallic base of a metal porcelain dental veneer,as with dental restorations, the gray color of the foil would prevent anatural looking veneer especially because veneers are thin.

It is known in the art that gold metal has a more esthetically pleasingcolor when used as a substructure in dental restorations. Gold coloredalloys, however, do not have sufficient tensile strength and hardness toserve as dental restoration substructures. One attempt to provide ametallic substructure having both suitable physical properties and anesthetically pleasing color involved a bimetallic backing having athicker layer of white colored alloy and a thinner layer of gold coloredalloy, as described in U.S. Pat. No. 2,572,377 issued Oct. 23, 1951 toR. E. O'Morrow. This backing disadvantageously requires the preparationand welding together of two distinct alloy materials.

It would be desirable to have for use in metal porcelain restorations,veneers and dental bridges, a foil having a color more similar to thatof natural dentin in order to facilitate matching the completerestoration with the surrounding natural teeth. It would further bedesirable to have a foil formed of a single alloy that is relativelyeasy to prepare. Furthermore, it would be desirable that the foil beheat resistant to minimize distortion when the overlaying porcelain isfired, yet sufficiently malleable to ensure proper fit of the foil tothe die, and ultimately of the finished restoration to the mouth.

Such a metal foil could be fashioned into the metal substrate of a metalporcelain dental restoration or dental bridges, or the metal base of ametal porcelain dental veneer by use of conventional techniques or bythe use of application of isostatic pressure as described in U.S. Pat.No. 4,794,774, issued Jan. 3, 1989, the complete disclosure of which isincorporated herein by reference.

SUMMARY OF THE INVENTION

The present invention thus provides a metal foil for use as asubstructure in a dental application. Specifically, the foil may be usedin metal-porcelain dental restorations, dental bridges and inmetal-porcelain dental veneers. The improved metal foil has superiorcolor characteristics and superior bonding to porcelain compared withprior art foils. Metal-porcelain dental restorations made with the foilhave improved aesthetic characteristics. Metal-porcelain dental veneersmade with the foil are more aesthetically pleasing, especially becausethe use of the foil prevents any interference of the underlying toothcolor or bonding material, is less expensive than such veneers made withcast metal, and are stronger and thinner than conventional all-ceramicveneers and thus occlusal and lingual as well as frontal and buccalveneers can be formed. Dental bridges that include copings made with thefoil have aesthetic and strength advantages. Metal-porcelain dentalbridges made with the metal and another layer of metal form unexpectedlystrong joints between the teeth on either side of the edentulous regionand the edentulous region itself.

The metal foil of the present invention also facilitates adhesion of theporcelain to the foil and has good heat resistance properties and goodmalleability.

The present invention overcomes the shortcomings of the prior art byproviding a metal foil of an alloy comprising gold, an amount ofplatinum or palladium, and an amount of a non-precious metal. Theplatinum or palladium and the non-precious metal serve to adjust thecolor of the gold to an aesthetically pleasing color when used withporcelain in metal-porcelain dental restorations. The platinum orpalladium is present in an amount sufficient to provide heat resistanceto minimize distortion when the porcelain is baked, yet low enough topreserve the malleability of the gold. The non-precious metal promoteschemical bonding of the porcelain to the foil without the need of abonding agent.

When used as an interior substructure for porcelain in a metal-porcelaindental restoration or dental bridge, the improved foil imparts superiorcolor to the finished restoration, and superior bonding between themetal and porcelain. When used as a coping for the base of a dentalbridge, the improved foil imparts superior color, fit, and strength tothe bridge. When used in a dental bridge with a second layer of the samefoil or of conventional foil, the joint strength is greatly enhanced.

When used as the base for porcelain in a metal porcelain dental veneer,the improved foil imparts superior color to the veneer, superior bondingbetween the metal and porcelain, and allows for a thinner, strongerveneer which can easily conceal even the most severe discoloration andcan be used occlusally and lingually.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this invention, reference shouldnow be made to the embodiment of the present invention illustrated ingreater detail in the accompanying drawings.

FIG. 1 is a schematic sectional view of a conventional veneer of theprior art.

FIG. 2 is a schematic sectional side view of an anterior dental veneerof the present invention.

FIG. 3 is a schematic sectional top view of the anterior veneer of FIG.2.

FIG. 4 is a schematic sectional view of a posterior occlusal veneer ofthe present invention.

FIG. 5 is a schematic sectional view of a lingual veneer of the presentinvention.

FIG. 6 is a schematic view of an edentulous region and the abutmentteeth.

FIG. 7 is a schematic view of a coping for the abutment teeth.

FIG. 8 is a schematic view of the pontic metal substructure affixed tothe copings.

FIG. 9 is a schematic lingual view of the pontic metal substructureafter the application of the opaque layer.

FIG. 10 is a schematic lingual view of a completed dental bridge.

FIG. 11 is a schematic labial view of a completed dental bridge.

FIG. 12 is a schematic occlusal sectional view of a two-layermetal-porcelain dental bridge.

FIG. 13 is a schematic sectional view of a two-layer metal porcelaindental bridge.

DETAILED DESCRIPTION

The following detailed description is illustrative of the best modepresently known for carrying out the invention, and is not to beinterpreted as limiting the disclosure.

In accordance with the invention, a metal foil which provides superiorcolor, malleability, and chemical bonding to the porcelain, as well asimproved heat resistance as compared with unalloyed gold is provided.The metal foil is formed of an alloy comprising at least about 88 wt. %gold, platinum or palladium, and a non-precious metal.

As is known in the art, color is characterized by its hue, chroma, andvalue. Hue relates to the location of the color along the visiblespectrum, that is, whether it is red, yellow, green, blue, brown, or soforth. Chroma, also known as saturation, relates to the intensity of thecolor, whether it is bright or pale. Value is the darkness or lightnessof a color, and is a function of the amount of light reflected. In thepresent invention, the relative amounts of the alloy constituents areproportioned to obtain the desired balance of hue, chroma, and value foran aesthetically pleasing dental restoration.

As is known in the art, the reddish-orange color of pure gold foil istoo red in hue as compared with the hue of the dentin of natural teeth.Also, the chroma of pure gold foil is undesirably high when comparedwith natural teeth. Adding a small amount of platinum alters the hue toa more acceptable yellowish shade closer to that of natural dentin. Theplatinum also reduces the chroma of the alloy. The platinum furtherimparts the advantages of improved heat resistance, whereby the foilwill be less likely to become distorted during the porcelain firingprocess. It has been found that at least about 0.5 wt. % platinum isdesirable to achieve these advantages. It is also preferred that theproportion of platinum should not exceed about 7 wt. %, in order topreserve the malleability of the foil when used with standardmanipulation techniques. About 1-6 wt. % platinum has been foundsatisfactory for most applications, and about 2-5 wt. % platinum appearsto give the best results. Palladium may be substituted for platinum withsimilar advantageous results, although care should be taken such thatthe palladium does not oxidize. Silver may also be substituted for theplatinum. Silver has a lower melting point than gold and a much lowermelting point than either platinum or palladium. The resulting alloywill therefore have a lower melting point, and will be suitable for usewith porcelains having lower fusion temperatures.

The incorporation of a non-precious metal imparts several advantages tothe foil. The non-precious metal reduces the amount of light reflectedfrom the foil, thus adjusting the value of the foil closer to that ofnatural dentin. Additionally, during firing of the porcelain-metalrestoration, wherein the porcelain paste is hardened, the non-preciousmetal at the surface of the foil will oxidize. The non-precious metaloxide also reacts with the porcelain, thereby promoting chemical bondingof the porcelain to the metal substructure, resulting in ametal-porcelain restoration of superior quality. At least about 0.1 wt.% non-precious metal is necessary to achieve the advantages of the valueadjustment and improved chemical bonding of the porcelain to the metalsubstructure. It has been found that at greater than about 5 wt. %non-precious metal the foil becomes too dark, and the thermal resistanceis also lessened. About 0.25-0.5 wt. % non-precious metal has been foundto be optimal for most applications. Suitable non-precious metalsinclude indium, iron, zinc, aluminum, copper and like metals thatreadily form oxides, are non-toxic, and are otherwise able to withstandthe chemical and physical environment of the human mouth.

Examples of alloys suitable for use in the instant invention are setforth in the following table. All numbers in the table indicate weightpercent.

    ______________________________________                                        Example   Gold         Platinum Indium                                        ______________________________________                                        1         97.75        2        0.25                                          2         97.5         2        0.5                                           3         97           2        1                                             4         95           2        3                                             5         94.75        5        0.25                                          6         94.5         5        0.5                                           7         94           5        1                                             8         92           5        3                                             ______________________________________                                    

The foil of the instant invention is prepared by first melting a desiredquantity of gold, melting a predetermined amount of platinum, palladiumor silver into the molten gold to obtain a molten alloy, and melting apredetermined quantity of a non-precious metal into the already moltenalloy. Those skilled in the metallurgical arts will recognize theappropriate temperatures and conditions for preparing such a moltenmetal alloy. Further it will be understood that the molten alloy can beprepared in an air atmosphere, in a vacuum, or in an argon atmosphere,as may be required by the various metals and the proportions of each ofthe metal components. The molten alloy is then cooled. The alloy is thenmade into a foil by standard rolling techniques that increase thedensity of the material, thereby improving the strength of the foil.Satisfactory results may be obtained with a foil 25-200 microns thick.The preferred thickness range of 50-100 microns gives a foil that issufficiently strong for this application yet thin enough to be easilyworkable.

As taught in the aforementioned U.S. Pat. No. 4,392,829, the finishedfoil may be sandblasted to provide a textured surface to which theporcelain will be applied. The textured surface provides microscopicsites for mechanical bonding of the porcelain to the foil. The foil maythen be used to make a superior metal-porcelain dental restoration bystandard methods or, for example, by the inventive method disclosed inU.S. Pat. No. 4,392,829 or the method disclosed in U.S. Pat. No.4,794,774. The improved metal-porcelain restoration will allow greaterease in color matching.

As seen in FIG. 1, a conventional prior art dental veneer 10 consists ofthree layers of porcelain, an opacified dentin porcelain layer 12, adentin porcelain layer 14 and an enamel porcelain layer 16. The totalthickness of the three layer porcelain veneer 10 is generally greaterthan 500 microns. The layers are applied to the tooth 18 by firstetching the surface 20 of the tooth 18. The veneer 10 is then bonded tothe surface 20 of tooth 18 using a bonding agent. The conventionalveneer 10 is formed in the laboratory and is subject to breakagewhenever it is handled in the preparation, shipping, and applicationsteps. Such conventional veneers do not posses good strengthcharacteristics and thus are generally only used in frontal and buccalapplications. Generally such conventional veneers are not used forocclusal or lingual veneers.

FIG. 2 shows an anterior veneer 30 made according to the presentinvention. The veneer 30 is made up of a layer 32 of metal which hasbaked thereon a layer 34 of opaque porcelain, a layer 36 of dentinporcelain and a layer 38 of enamel porcelain. FIG. 3 is a schematic topsectional view of the anterior veneer 30 of FIG. 2. The layer of metal32 as well as layer 36 of dentin porcelain can be seen. The veneer 30,is bonded to tooth 40 as described below. Because metal layer 32 iscompletely opaque, the color of the bonding agent does not effect thecolor of the finished veneer.

In a preferred embodiment, the metal 32 is a metal foil of thecomposition previously set forth. More preferably, the layer 32 is sucha metal foil which has been formed under isostatic pressure in a waysimilar to the method described in U.S. Pat. No. 4,794,774 and thesurface of the foil is texturized as described in U.S. Pat. No.4,392,829. Most preferably, the layer 32 is prepared as disclosed aboveand is approximately 50 microns thick. Preferably, the combination ofthe metal layer 32 and the opaque porcelain layer 34 is approximately150 microns thick. The combination of the dentin porcelain layer 36 andthe enamel porcelain layer 38 is preferably approximately 200 micronsthick. Thus, the entire veneer 30 is less than 500 microns thick.

Even though veneer 30 is only 350 microns thick, the use of the improvedmetal foil as foil layer 32 results in a veneer 30 which is more naturalin appearance than prior art veneers, is shadewise more controllable,covers all discoloration on the underlying tooth, and is stronger whencompared to the prior art veneer.

Because of the strength of veneers made according to the presentinvention, it is possible to fabricate posterior occlusal veneers asseen in FIG. 4 and lingual veneers as seen in FIG. 5. A posteriorocclusal veneer 50 is shown in FIG. 4 with a layer 52 of metal and alayer 54 of opaque porcelain. A lingual veneer 60 as in FIG. 5 is madefrom a layer 62 of metal and a layer 64 of opaque porcelain. The use ofthe metal as a base provides strength and the use of the particularmetal of this invention allows the veneer to be aesthetically pleasing.

The veneers of the present invention are bonded to the underlying toothusing a bonding material. Before bonding, the surface of the tooth isetched to provide added adhesion. The preferred bonding material is a4-Metacrylate resin sold under the trademark Superbond by Rocky MountainMorita Co. and Certainbond by Rocky Mountain Orthodontics. Afteretching, the bonding agent comprising a monomer and catalyst is mixedand applied to the surface of the metal. Additional monomer is appliedto the surface of the tooth, the veneer is seated and the bonding agentcures, creating a strong sure bond.

A porcelain dental restoration of the type referred to as a dentalbridge is also advantageous formed of the metal foil of this inventionas follows.

Referring to FIG. 6, the two abutment teeth 112 and 114 on either sideof the edentulous region 116 are ground down to posts. Although theabutment teeth 112 and 114 will be generally smooth after grinding theywill not be of uniform shape or configuration, and the dental bridgemust be specially designed to fit the exact shape and configuration ofthe abutment teeth.

As shown in FIG. 7, a metal foil coping 122 is formed for use onabutment tooth 112 (correspondingly, another coping, not shown, isformed for use on abutment tooth 114). This coping facilitates a closefit between the abutment teeth and the dental bridge by fitting exactlyto the shape of the abutment teeth. The coping is made of the foildescribed above in order to provide an aesthetically pleasing margin orinterface between the reconstruction and the adjacent gums. Moreover, ithas been found that gingival tissue responds more favorably to the foilof this invention than to prior art foils. Preferably, the coping ismade using the method disclosed in U.S. Pat. No. 4,794,774 in order toproduce copings which are closely formed and has a good bond with theabutment teeth.

A metal pontic substructure 130, as shown in FIG. 8, is prepared byconventional lost wax technique. The copings 122 and 124 (for abutmentteeth 112 and 114 respectively) are connected to the cast metal ponticsubstructure 130 with glue which will burn out when the opaque is baked.Consequently, a glue that will burn at a temperature less than thebaking temperature of the opaque is required. Connections between thecopings 122 and 124 and the metal pontic substructure 130 can also beaccomplished by electric welding. Because the pontic substructure 130 isbeing connected to the copings 122 and 124 which can be made of auniform shape, the connection is stronger than that used in the priorart where the substructure was connected directly to the abutment teethwithout use of a coping. Thus, in the prior art, the pontic substructurehad to be formed more carefully and still did not achieve the bondingstrength of a bridge using copings formed from the improved metal foil.

As seen in FIG. 9 an opaque layer is then applied and the bridge 140 isbuilt up using conventional ceramic method. After the opaque layer isapplied, the glue is no longer necessary. The opaque layer holds thepositions of the copings 122, 124 and the cast metal pontic substructure130.

The opaque layer provides a base for the ceramic buildup comprising thereconstructions, as shown in FIGS. 10 and 11. Conventional methods canbe used to reconstruct the abutment teeth 112 and 114 to obtainreconstructed teeth 142 and 144 respectively and to construct a tooth146 in what used to be the edentulous region 116. As seen in FIG. 11,the metal copings 122 and 124 are visible between the reconstructedteeth 142 and 144 and the adjacent gums 150. While any dental foil canbe used to make the copings use of the improved metal foil of thisinvention for the copings will provide an aesthetically pleasinginterface or margin and allow the patient to smile normally withoutfeeling self-conscious.

Referring to FIGS. 12 and 13, a second embodiment of a dental bridgewhich uses the improved metal foil of the invention is disclosed. Ratherthan forming copings on the abutment teeth the metal foil of thisinvention can be advantageously used in a second manner to form a dentalbridge.

Referring to FIG. 12, the two abutment teeth 212 and 214 are seen.Rather than grinding the abutment teeth to posts, only the lingualsurface of abutment teeth 212 and 214 need to be ground, to producegenerally flat bonding surfaces 222 and 224 respectively. A bridge 230can then be formed by bonding a metal foil 238 to the generally flatsurfaces 222 and 224 of abutment teeth 212 and 214. In order to getsufficient strength for the bridge, the bond between layer 238 andsurfaces 222 and 224 must be tight and firm and the ceramic materialmust bond well to the foil. Thus, the improved metal of the presentinvention is used for metal foil layer 238 to provide the improvedbonding characteristics as described above. This layer 238 is bonded tosurfaces 222 and 224 as described above with respect to the bonding ofdental veneers. The layer 238 extends through the edentulous region andforms the base for a traditional ceramic buildup to construct tooth 246in the previously edentulous region.

It is known from prior art all ceramic bridges that the joint areas, thearea between an abutment tooth and the previously edentulous regioncontaining the ceramic restoration is particularly prone to breakage.Thus, as seen in FIG. 12, after an amount of ceramic material 248 isbuilt up on metal foil layer 238 a second foil layer 258 is added.Generally, the ceramic material 248 between metal layers 238 and 258would be from about 0.1 to about 0.3 millimeters thick. The second foillayer 258 can extend the entire length of the bridge as shown in FIG. 12or could be used only in joint areas 252 and 254, extending onlyslightly past the joint areas. This second foil layer 258 can be theimproved metal foil of this invention or it can be a conventional foil.The second foil layer does not have to be as malleable as the firstlayer because it does not have to fit as closely to the adjacent ceramiclayers. Depending on the particular application, one of ordinary skillwill know to choose the metal to advantageously enhance the strengthcharacteristics of the bridge. One skilled in the art will recognizethat if differing metals are used for layers 238 and 258 the expansioncharacteristics of the two metals and the ceramic must be matched so asnot to unnecessarily stress and perhaps break the bridge 230 inmanufacture or use.

FIG. 13 shows another two-layer bridge 330 of the present invention.This shows an application of the two-layer concept to a posteriorbridge. In such a case, the abutment teeth 312 and 314 are ground downfrom the top to form surfaces 322 and 324. These surfaces may besubstantially flat or, as shown, may contain notches 332 and 334 toimpart added stability, strength and bonding. A layer 338 of the metalfoil of this invention is bonded to surfaces 322 and 324. Again, anamount of ceramic material 348 as previously described is added and asecond foil layer 358 is added. As described before this second layer358 can extent throughout bridge 330 or can be located only aroundjoints 352 and 354. Conventional methods are used to construct tooth 346in the previously edentulous region and to reconstruct the occlusalsurfaces of 342 and 344 of abutment teeth 312 and 314.

The use of the second foil layer 258 or 358 unexpectedly result injoints four times as strong as corresponding joints in a dental bridgemade with only one layer of metal.

Obviously, many modifications and other embodiments of the subjectinvention will be recognized by one skilled in the art in view of theforegoing teachings. For example, while the disclosed alloy has beendescribed as used in a foil substructure, it may also find utility as acast substructure for dental restorations. Therefore, the invention isnot to be limited thereto and any modifications are intended to beincluded within the scope of the appended claims

What is claimed is:
 1. A metal-porcelain dental restoration for fillingan edentulous region comprising:(a) a first layer of a thin metal foilclosely fitting the contours of the two abutment teeth on either side ofthe edentulous regions; (b) a layer of ceramic on said first metal foillayer; (c) a second layer of a thin metal foil connected to said ceramiclayer, said second layer extending at least across the joint from saidabutment teeth to said edentulous region; and (d) a ceramic build-up tofill said edentulous region.
 2. The metal-porcelain dental restorationof claim 1 wherein said first metal foil layer comprises a metal foilcomprising a three-component alloy consisting of a total of about 2-5wt. % of a color-adjusting metal from the group consisting of platinum,palladium, and silver; a total of about 0.1-5 wt. % of a non-preciousmetal from the group consisting of indium, iron, zinc, aluminum, andcopper; and the balance gold.
 3. The metal-porcelain dental restorationof claim 2 wherein said first metal foil layer comprises a metal foilcomprising about 3 wt. % platinum and about 0.25 wt. % indium.
 4. Themetal-porcelain dental restoration of claim 2 wherein said second metalfoil layer comprises a metal foil comprising a three-component alloyconsisting of a total of about 2-5 wt. % of a color-adjusting metal fromthe group consisting of platinum, palladium, and silver; a total ofabout 0.1-5 wt. % of a non-precious metal from the group consisting ofindium, iron, zinc, aluminum and copper; and the balance gold.
 5. Themetal-porcelain dental restoration of claim 4 wherein both said firstmetal foil layer and said second foil layer comprise a metal foilcomprising about 3 wt. % platinum and 0.25 wt. % indium.